Juvenile coho (Oncorhynchus kisutch) will spawn and have their offspring reared in very
different habitat types in coastal British Columbian streams. For instance, some utilize main
channel river areas whereas others take advantage of off-channel habitats. However, during
winter, juveniles produced in the main channel areas are believed to move into off-channel
habitats for reasons of protection. These main channel juveniles tend to be much larger at the
start of winter than the off-channel resident juveniles. It is possible that these two size morphs
reflect genetic differentiation that would indicate either the fine-scale population structure or
heritable growth-related differences between individuals using different habitats. On the other
hand, the variation may simply reflect phenotypic plasticity. There is little understanding of the
correspondence between neutral molecular genetic variation and adaptive variation, yet patterns
of molecular variation are most often used to develop management plans directed towards
conserving genetic diversity in salmon populations. This study describes variation for both
microsatellites (neutral genetic markers) and growth, presumably an adaptive trait, in closely
located populations of coho salmon.
The genetic basis of the observed size variation was explored by studying juvenile coho from the
Mamquam River. After 6 months rearing in a common environment, no size differences were
observed between juveniles originating from different habitats. More variation for size was
observed between individuals sampled from within habitat types than was observed among
habitats. This result suggested that the size variation is a result of phenotypic plasticity
associated with environmental differences in rearing habitat. It does not exclude the possibility
that variation for growth among individuals is associated with adaptive differences on a
microhabitat scale. Microsatellite analysis revealed fine-scale population structure within the
Mamquam River resulting from either founder effects associated with channel colonisation, the
existence of separate races, or sampling bias. Heritability for growth over the six-month rearing
period and size were estimated by a novel technique that uses molecular marker similarity to
infer relatedness. Positive co-variances were observed between relatedness and phenotypic
similarity for growth rate and initial size indicating heritability for these traits.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/9270 |
| Date | 11 1900 |
| Creators | Dobson, Diana |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
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